Prime Minister Yoshiro Mori has decided to convene the regular 150-day session of the Diet on Jan. 31, setting the stage for Upper House elections at the end of July.
Mori reached the decision Monday in a meeting with senior members of his Liberal Democratic Party, LDP officials said.
A Jan. 31 opening would mean closure on June 29, provided there are no extensions.
As the terms of Upper House members whose seats are up for grabs end on July 22, the chamber's next election would have to be held within 24 to 30 days of the session's close, making it likely the poll will be held July 29, the only Sunday in that period.
Elections are customarily held on Sundays.
In the next regular session, lawmakers are expected to deliberate the budget for the fiscal year beginning in April as well as bills on education reform, one of Mori's pet projects.